ABSTRACT
Plasmid-mediated and chromosomally-encoded colistin resistance is increasingly being reported worldwide. We aimed to determine the prevalence of faecal carriage of colistin-resistant Gram-negative rod isolates in a university hospital in western France. From February to May 2016, rectal swabs from 653 patients hospitalized in various clinical settings were recovered and subsequently screened for colistin resistance using the SuperPolymyxin medium. Antimicrobial susceptibilities were determined according to EUCAST guidelines. Genetic detection of plasmid-mediated colistin resistance was performed by PCR. The faecal carriage with intrinsic colistin-resistant isolates was high (23â%), while the faecal carriage with Gram-negative rods showing acquired resistance was low (1.4â%). No isolate carried the plasmid-mediated mcr-1/mcr-2 genes. It was noteworthy that none of the patients carrying isolates with acquired colistin resistance had previously received a colistin-based treatment, while these isolates were not multidrug resistant.
Subject(s)
Anti-Bacterial Agents/pharmacology , Carrier State/microbiology , Colistin/pharmacology , Feces/microbiology , Gram-Negative Bacteria/isolation & purification , Gram-Negative Bacterial Infections/microbiology , Carrier State/epidemiology , Drug Resistance, Bacterial/genetics , France/epidemiology , Gram-Negative Bacteria/drug effects , Gram-Negative Bacteria/genetics , Gram-Negative Bacterial Infections/epidemiology , Hospitals, University , Humans , Microbial Sensitivity Tests , Polymerase Chain Reaction , PrevalenceABSTRACT
Objectives: To determine the susceptibility to colistin of Hafnia alvei and Hafnia paralvei, and to compare methods for colistin resistance detection in the Hafnia genus. Methods: A collection of 25 Hafnia isolates was studied. Species were identified by using 16S rRNA gene sequencing with subsequent phylogeny analysis. Susceptibility to colistin was determined using the broth microdilution (BMD) reference method, the Phoenix automated system, the Rapid Polymyxin NP test, the Etest system and the disc diffusion method. Results: The collection consisted of 15 H. alvei and 10 H. paralvei isolates. Based on the 16S rRNA analysis, a close relationship of the Hafnia genus with naturally colistin-resistant enterobacterial genera (Proteus, Morganella, Providencia and Serratia) was identified. Susceptibility testing performed using the BMD method, the Phoenix automated system and the Rapid Polymyxin NP test revealed a high rate of colistin resistance (96%). Underestimation of colistin resistance using Etest strips (72%) and the disc diffusion method (0%) was observed. Conclusions: The high rate of colistin resistance observed within the Hafnia genus and its close phylogenetic relationship with naturally colistin-resistant genera suggest that Hafnia is a naturally colistin-resistant enterobacterial genus.
